Basement and foundation waterproofing is a critical aspect of the construction of new buildings. The waterproofing process generally involves applying a composition to a wall to impart water resistant properties. Prior art coatings included asphalts dissolved in a solvent which are sprayed onto a wall. It is common to apply a protective board over the coating for facilitating water drainage and/or providing additional insulation.
In addition to superior water resistant characteristics, good basement wall coatings require a variety of properties in order to be considered satisfactory. They should be strong, have good elasticity, and be able to be applied uniformly to the surface of a wall. While asphalt based compositions have performed satisfactorily, polymer based compositions are also particularly useful for waterproofing. Since polymer based coatings usually have more than one solid ingredient in the formulation, it is important that all ingredients be chemically compatible to avoid separation of the polymer components from the solution resulting in loss of the desirable properties of the solution. Such separation can cause loss of elasticity, strength, tack, and water resistance.
In many waterproofing applications it is generally preferred to apply a protective board while the coating is still. wet. In some cases, however, this is not possible. Therefore, it is desirable for the coating to maintain aggressive residual tack, even when the coating is dry. Without sufficient tack, the waterproofer must often resort to mechanical fasteners such as nails to hold the protective board to the wall. Such mechanical fasteners put holes in the coating, jeopardizing its waterproofing ability.
When using a coating comprised of polymeric materials, it is important that there be a proper physicochemical interaction between the polymers and the solvent. The solvent must be able to dissolve the various polymers as well as impart additional characteristics to the composition as a whole. Such properties are unique to the solvent system itself as will be explained herein.
A satisfactory coating should also provide a consistent, uniform coating on the wall. The solvent is believed to be related to the consistency of the coating applied to the wall. Coating that runs down the wall during application may lead to weak spots in the coating. The solvent also affects the drying rate of the coating. When the prior art coatings cure too quickly due to factors such as elevated temperatures or exposure to sunlight, trapped air may cause pinholes in the coating surface, as the air escapes from the coating. The rupturing of such pin holes also leads to weak spots in the coating. Therefore, there is a need in the prior art for a solvent system, which eliminates aeration and allows for the release of trapped air from the coating irrespective of the rate at which the coating dries.
Solvent systems used in prior art coatings are generally highly explosive and flammable. For example, U.S. Pat. No. 5,352,531 to Roberts recommends using combinations of an aliphatic petroleum distillate, such as LACOLENE sold by Ashland Chemical Company, and toluene. Such a solvent has a flash point of about 18° F. As another example, U.S. Pat. No. 5,932,646 to Roberts uses a solvent that is a blend of petroleum distillates, preferably naphthenic distillates, and heptane. A solvent recommended in this patent is sold by UNOCAL under the name Lactol Spirits. This solvent has a flash point of about 17° F. As a result of the extremely low flash points, solutions including these solvents are highly explosive. Thus, they are very dangerous to use as the slightest spark may ignite the vapors around the material, Chlorinated organic solvents have not previously been used in waterproofing applications, likely because their use was believed to be cost prohibitive.
In addition, the prior art compositions exhibited a very low viscosity at spraying temperatures snaking sag and run down more likely until the material cooled and began to dry. Waterproofing compositions that have a lower viscosity at spraying temperature also require the application of more coats of the composition to achieve the desired thickness of the waterproofing material.
Elastomeric, emulsion-based coatings, which includes water-based acrylic polymer coating systems, currently dominate the roof coating market. Oil-based products have been almost completely replaced by water based products due to their volatile organic content (VOC). Oil-based products have historically not been deemed suitable for roof coatings because of their need for a carrier solvent that typically is a VOC material and composes 40% to 60% of the coating formulation. Currently, environmental laws in California allow 2.3 pounds per gallon of V.O.C., or a limit of 18% V.O.C.
The Environmental Protection Agency (EPA) oversees the “Energy Star” program. Energy Star is an international standard for energy efficient consumer products. It was first created as a United States government program in 1992. In order for a coating to receive the “Energy Star Approval,” for example, a roof coating must maintain a reflectance of over “65” after three years of outdoor weathering. The reflectivity requirement is based on the fact that a white, reflective coating will reflect the heat produced by the sun and dramatically lower the amount of heat developed on the roof surface of the building. The less amount of heat that is produced by the roof will typically result in lower air conditioning costs and a significant reductions in electrical usage which is generated by highly polluting coal fired plants.
The inability to meet the EPA and VOC standards have been major obstacles to the use of previous oil based coatings for roof coatings. The use of flammable solvents, poor fire ratings, susceptibility to mold and fungal growth, formation of a skin in the container and the need for heavy metals to cure the coating have prevented these oil-based coatings from being recognized as Energy Star products.
Thus, a need exists for an improved coating system for use in waterproofing applications, which is capable of dissolving rubber and polymer-based waterproofing compositions to allow them to be applied on roofs that are non-flammable and qualify for Energy Star approval.